Hooking up in line fans to boost temperature in one room

[simonmason]

My Comfortmaker system was installed and two in line fans were added to boost the output to one room. The fans were wired to an always on AC connection and as far as I can tell have both burned out over time. I am about to replace them and I see two options - hook them to an AC line that receives power when the furnace is running or hook them to duct stats. My preference is to do the first because it is cleaner, less things to go wrong. I cannot find any documentation on my furnace so I was wondering if anyone had any links to information that will help me figure out if there is a switched 110v coming off the furnace for running accessories? Thanks.

[Chris_Worthington]

Thread relocated to AOP

[heaterman]

Care should be taken not to exceed the amp capacity of any control boards or controls on your furnace. Doing so will cause over loads resulting in failures that will be expensive. There are several ways to achieve what you want but site rules prevent any detailed DIY instructions. Any competent local HVAC professional should be able to help you with this.

[motoguy128]

Two inline fans to boost output to a single room?

Has anything else been done to balance the system?

Duct fans should be a last resort after everythign else has been tried.

Fantech makes some good quality inline mixed flow fans. I have one in my home exhausting my garage that's going on 1-1/2 years running continously.

I would power it seperate of the furnance and use a relay triggered by the "EAC" output on the furnace board so it runs when the furnace blower runs only.

[simonmason]

Thanks for the help. The relay sounds like the way to go. I don't want the fans running all of the time as it will reduce their life and consume electricity. The room is on the outside of the house - a converted porch - with windows on three walls - so it is always cold or hot depending on the season. I am not sure why two fans were installed - I will try hooking them up one at a time.

Two inline fans to boost output to a single room?

Has anything else been done to balance the system?

Duct fans should be a last resort after everythign else has been tried.

Fantech makes some good quality inline mixed flow fans. I have one in my home exhausting my garage that's going on 1-1/2 years running continously.

I would power it seperate of the furnance and use a relay triggered by the "EAC" output on the furnace board so it runs when the furnace blower runs only.

[Shophound]

Did the room ever stay comfortable when the booster fans worked?

[fliks]

I have used pressure or sail switches. If their is poor return with door shut an additional return would probably help.

[simonmason]

I can't remember. I don't know how long it has been since the fans have been working. The room is always cold.

Did the room ever stay comfortable when the booster fans worked?

[Hiptech]

I can't remember. I don't know how long it has been since the fans have been working. The room is always cold.

Think I would spend my time and money on insulating and draft-sealing the room. Converted porch will never be comfortable unless these issues are addressed first, especially with that amount of windows. Boost fans alone will not do the trick.
More than likely insulation is poor at best, that is where I would look first, if you want to actually make the room usable.

Hiptech

[catmanacman]

perfect solution would be a ductless mini split

[simonmason]

Thanks for all of the help. I agree that the mini split would be a good solution - albeit a lot more expensive than two duct fans! The room was done properly - insulated, etc. However, it is cold because it is on the outside wall of the house and has casement windows going from 18" above the floor to the ceiling on three walls. So there wasn't much room for insulation except around the bottom of the walls and in the ceiling. There is no return in the room - the closest return is in the next room. The room is mostly laid on a concrete slab although there is access underneath at one end of the room. Would adding a return make much of a difference?

[catmanacman]

is the room closed off from the rest of the house or is there a cased opening .if it's closed off it needs a return

[simonmason]

It has a pocket door into the house and this is always open. The return is just through the pocket door.

[kdean1]

Wouldn't a properly sized supply run solve the whole thing?

[Shophound]

I can't remember. I don't know how long it has been since the fans have been working. The room is always cold.

If you cannot remember the room ever being warm, either rhe booster fans have been burned out forever, or they never did any good in the first place. My money would be on the latter bet. Furthermore, I would bet that if you pulled the booster fans out of the duct and then patched the duct where the fans were, the room might actually feel a little warmer. Not much, but more than you have had so far.

By how you describe the addition, it is a huge heat loser, and you do not have enough warm air going in to offset the loss. Mimi split is probably your best option, since your existing house system might not handle a room with that high of a heat loss.

[simonmason]

I am trying to zero in on a solution here. I looked at the system board - it is a Comfortmaker C8MPN100F14B1. I do see markings for EAC but there appears to be no connector. Same is true for the CONT FAN next to it. I am assuming that this model did not have this option installed. I see a what I thinks is a relay right next to it with an open NC or NO. I am assuming this is a low voltage relay, but assuming it triggers when the furnace runs I might be able to do something with this? I put pictures below of what I am seeing. Thanks for the direction.

http://postimage.org/image/c7ph2vhpf/
http://postimage.org/image/ov9tt4m03/

[54regcab]

Booster fans rarely solve the issue. Unless the ductwork is inaccessible it needs to be corrected. The minisplit would be the best solution.

[simonmason]

The mini split is not in the budget at this point. The two ducts supplying the room are underneath the concrete slab. There is the possibility of adding a return although there is one in the room next door right next to the door. In theory, more air into the room would raise the temperature? All I need to try this is to figure out the best way to kick in the fans so that they don't run all of the time.

[jtrammel]

In line fans usually slow air flow rather than boost it. It just acts as a restriction in the duct. Look into ptac unit (like in hotel rooms) they are much cheaper than mini splits and work well for sunrooms.

[simonmason]

So pull out fans and go with separate unit?